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1 | #include <linux/ptrace.h> |
2 | #include <linux/sched.h> |
3 | #include <linux/export.h> |
4 | #include <asm/syscall.h> |
5 | |
6 | static int collect_syscall(struct task_struct *target, long *callno, |
7 | unsigned long args[6], unsigned int maxargs, |
8 | unsigned long *sp, unsigned long *pc) |
9 | { |
10 | struct pt_regs *regs = task_pt_regs(target); |
11 | if (unlikely(!regs)) |
12 | return -EAGAIN; |
13 | |
14 | *sp = user_stack_pointer(regs); |
15 | *pc = instruction_pointer(regs); |
16 | |
17 | *callno = syscall_get_nr(target, regs); |
18 | if (*callno != -1L && maxargs > 0) |
19 | syscall_get_arguments(target, regs, 0, maxargs, args); |
20 | |
21 | return 0; |
22 | } |
23 | |
24 | /** |
25 | * task_current_syscall - Discover what a blocked task is doing. |
26 | * @target: thread to examine |
27 | * @callno: filled with system call number or -1 |
28 | * @args: filled with @maxargs system call arguments |
29 | * @maxargs: number of elements in @args to fill |
30 | * @sp: filled with user stack pointer |
31 | * @pc: filled with user PC |
32 | * |
33 | * If @target is blocked in a system call, returns zero with *@callno |
34 | * set to the the call's number and @args filled in with its arguments. |
35 | * Registers not used for system call arguments may not be available and |
36 | * it is not kosher to use &struct user_regset calls while the system |
37 | * call is still in progress. Note we may get this result if @target |
38 | * has finished its system call but not yet returned to user mode, such |
39 | * as when it's stopped for signal handling or syscall exit tracing. |
40 | * |
41 | * If @target is blocked in the kernel during a fault or exception, |
42 | * returns zero with *@callno set to -1 and does not fill in @args. |
43 | * If so, it's now safe to examine @target using &struct user_regset |
44 | * get() calls as long as we're sure @target won't return to user mode. |
45 | * |
46 | * Returns -%EAGAIN if @target does not remain blocked. |
47 | * |
48 | * Returns -%EINVAL if @maxargs is too large (maximum is six). |
49 | */ |
50 | int task_current_syscall(struct task_struct *target, long *callno, |
51 | unsigned long args[6], unsigned int maxargs, |
52 | unsigned long *sp, unsigned long *pc) |
53 | { |
54 | long state; |
55 | unsigned long ncsw; |
56 | |
57 | if (unlikely(maxargs > 6)) |
58 | return -EINVAL; |
59 | |
60 | if (target == current) |
61 | return collect_syscall(target, callno, args, maxargs, sp, pc); |
62 | |
63 | state = target->state; |
64 | if (unlikely(!state)) |
65 | return -EAGAIN; |
66 | |
67 | ncsw = wait_task_inactive(target, state); |
68 | if (unlikely(!ncsw) || |
69 | unlikely(collect_syscall(target, callno, args, maxargs, sp, pc)) || |
70 | unlikely(wait_task_inactive(target, state) != ncsw)) |
71 | return -EAGAIN; |
72 | |
73 | return 0; |
74 | } |
75 | EXPORT_SYMBOL_GPL(task_current_syscall); |
76 |
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Tags:
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v2.6.34-rc5
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